1. Technical Field
The present disclosure relates to a semiconductor light emitting devices, and more particularly to ridge-type semiconductor lasers and methods for manufacturing same.
2. Description of the Related Art
Semiconductor lasers have been used for diversifying purposes, including optical communications, welding, and medical care in industrial use; and optical disks in commercial use. Many semiconductor lasers adopt a real-guide structure that can easily achieve both improved efficiency of current injection to an active layer and stabilization of lateral mode. There are many ways to obtain the real-guide structure, including buried type and ridge type. With respect to cost reduction and easy manufacture of semiconductor laser, the ridge type is often adopted.
FIG. 6 illustrates the structure of a conventional ridge-type semiconductor laser (Japanese Patent Publication No. 3242967, FIG. 1).
In the structure of the ridge-type semiconductor laser shown in FIG. 6, from p-type GaInP cap layer 108 to p-type AlGaInP clad layer 107 are etched to process a ridge shape. Here, p-type GaInP etching stop layer 106 shown in FIG. 6 is provided between p-type AlGaInP clad layer 105 and p-type AlGaInP clad layer 107. In the conventional method, etching is completed before p-type AlGaInP clad layer 105 is etched, using the condition that an etching rate of p-type GaInP etching stop layer 106 is smaller than an etching rate of p-type AGaInP clad layer 107, in order not to etch p-type GaInP clad layer 105 in an etching process. The etching rate is mainly adjusted by adjusting Al composition in each layer. Normally, if the Al composition is high, the etching rate becomes larger. If the Al composition is low, the etching rate becomes smaller. Therefore, to secure a sufficient difference in etching rates, the conventional ridge-type semiconductor laser uses p-type GaInP without Al as the etching stop layer for securing an etching selectivity with p-type AlGaInP clad layer 107.